Suspected penicillin allergy is common among hospitalised patients, but the quality of the information given by the patient is often doubtful. Alleged penicillin allergics are likely to be treated with more toxic, broad-spectered, and more expensive antibiotics, with effects on microbial resistance patterns and public economy as a consequence. We performed a cross-sectional case-control study with two visits to all clinical departments of a large university hospital in order to find in-patients with medical files labelled ''penicillin allergy'' or who reported penicillin allergy upon admission. Patient histories were obtained via a questionnaire, and they were offered investigation for penicillin allergy with specific IgE, basophil histamine release, skin prick tests, intradermal tests and drug challenge tests. Finally, the pharmaco-economical consequences of the penicillin allergy were estimated. In a cohort of 3642 patients, 96 fulfilled the inclusion criteria giving a point-prevalence of alleged penicillin allergy of 5% in a hospital in-patient population. Mean time elapsed since the alleged first reaction to penicillin was 20 years. The skin was the most frequently affected organ (82.2%), maculo-papular exanthema (35.4%) and urticaria (10.4%) being the most frequently reported reactions. 25% did not recall the time of their reaction. 82.2% did not remember the name of the penicillin they reacted to. 34.8% had been treated with penicillins after suspicion of penicillin allergy had been raised. None of these reacted to penicillins. 33.3% of the patients receiving antibiotics during their current hospitalisation were prescribed penicillins. 2% developed non-severe exanthema. The average acquisition costs for antibiotics to penicillin allergic patients were s 278, compared to s 119 had they been nonallergics. The prevalence of suspected penicillin allergy was lower than reported elsewhere. A substantial number of patients failed to recall basic information about their alleged allergy. Patients reporting penicillin allergy upon admission and labels stating penicillin allergy on medical files are ignored in almost a third of patients receiving antibiotics. The acquisition costs for antibiotics to penicillin allergic patients were higher, compared to the cost had the patients been nonallergics.

Many patients experience reactions during penicillin treatment. The diagnosis may be difficult and is mainly based on short-term tests. The European Network for Drug Allergy (ENDA) guidelines proposed for diagnosing penicillin allergy do not include long-term challenge. In this study a total of 405 patients were evaluated. The ENDA guidelines were extended, to include a 7-day oral treatment (p.o.7) with penicillin for all patients who were negative in the ENDA programme. Among the 405 patients; 85 had an immediate reaction to penicillin, and a further 13 reacted during p.o.7. Among the 307 patients with a negative outcome, 88 had a case history of reaction to other β-lactam antibiotics and were subsequently tested with the culprit drug. Thirteen patients had a positive outcome: 3 on single-dose challenge and 10 during p.o.7. The extended penicillin diagnostic work-up was positive in 111 patients, 30.0% showed immediate reactions and 5.7% reacted during p.o.7. Approximately 20% of all patients with positive outcome during penicillin challenge are detected by adding p.o.7 with penicillin to the original ENDA guidelines.

Patients with suspected cutaneous adverse drug reactions are often referred to allergy clinics or departments of dermatology for evaluation. These patients are selected compared with patients identified in prospective and cross-sectional studies of hospital populations. This explains the observed variation in prevalence of specific reactions and of eliciting drugs. This study investigated the prevalence of cutaneous adverse drug reactions in a university hospital department of dermatology that is specially focused on allergy. An 8-month survey was carried out during the period April-December 2003. Consecutive patients suspected of having cutaneous adverse drug reactions during this period were examined by dermatologists and investigated. Drug imputability was assessed in the 194 patients included; 33.5% had an exanthema with certain or likely drug imputability. Urticaria and local reactions at injection sites were the most frequent reactions (25% and 18.8%, respectively). Beta-lactam antibiotics, extracts for desensitization and insulins were the main drug groups involved, and accounted for 22.8%, 17.1% and 14.2%, respectively, of the reactions. Extracts for desensitization and insulins elicited more reactions than expected. This probably reflects the referral pattern to an allergy clinic.

Background: Drug challenge test (DCT) has long been the most sensitive test in the allergological work-up when investigating for penicillin allergy. Objective: To improve sensitivity of the diagnostic work-up in diagnosing penicillin allergics with histories of allergic reactions on day 2 or later in the course of penicillin treatment. Methods: A full-course DCT was added to the current protocol if specific IgE, skin tests and DCT were all negative in patients who had a nonimmediate reaction to penicillin treatment. Sixteen patients with a history of an immediate reaction to penicillin treatment underwent testing with negative outcomes. Results: Fifty percent of patients undergoing full-course DCT experienced a cutaneous adverse drug reaction. None of the controls reacted (p = 0.001). The mean time of reaction was 6 days. Penicillin V accounted for most reactions. Urticaria was the most frequent clinical reaction observed. Conclusions: Full-course DCT offers an improvement of sensitivity and predictive values of the diagnostic work-up of allergic reactions to penicillin occurring on day 2 of penicillin treatment or later.